Field Background won't change back

I made a script to change the background to RED is the value was less than 4 AND greater than 0.

The changing to RED works great.  Problem is when it changes to anything above 4 it stays RED and wont' go back to Orange.

var G5= this.getField("G5").value;

var C7= this.getField("C7").value;

var C8= this.getField("C8").value;

if((C8*G5)==0)

{

event.value=(C7);

}else{

event.value=(((G5/C8)/5280)*3600);

}

(function (){

if (event.value<4 && event.value>0)event.target.fillColor=color.red;

else

event.target.fillColor=color.orange;

})();